1. Field of the Invention
The present invention is directed to systems for access control and object identification. More particularly, embodiments of the present invention are directed to radio frequency (RF) identification systems employing an electronic transponder and a transponder reader which emits an RF interrogation signal at a first frequency which powers the electronic transponder and enables it to transmit a response on a second frequency (usually a lower frequency). More particularly, the system is used to read a characteristic of an object such as the electronic transponder using a Radio Frequency Identification (RFID) System, such reader employing a detector to detect the presence of the object within the field of inspection and generating a first signal in response thereto. Such systems are used in a number of fields including access security, object identification, inventory control, and generally any field where a small transponder unit may be associated with an object and remotely probed and read by a radio frequency transmission emitted by a transponder reader.
2. The Background Art
Radio frequency identification systems are well known in the art. Such systems are commonly in use in building access schemes where an authorized user of the building is given a building access card containing an authorization code number stored and optionally encrypted on the card as a binary string of data. The card is then presented to an transponder electronic reader which continuously transmits an RF interrogation signal. The card containing a transponder object receives the continuously transmitted signal from the electronic reader, uses it to power circuitry on board the card object, modulate an RF carrier signal having a different frequency (usually lower) from that of the RF interrogation signal received from the reader (typically an integer fraction of the RF interrogation signal frequency, e.g., xc2xd, ⅓, xc2xc, etc.) with an identification signal stored on the transponder object and containing an authorization code number, and the transponder electronic reader then reads the identification signal emitted from the transponder object and passes the authorization code number to an appropriate controller for determining whether or not the authorization code number received is sufficient to allow the user access to the building. If the authorization code number is sufficient, generally a lock will be opened enabling a door to be opened and optionally a computer will log the entry for future reference.
Other implementations of such systems enable object identification by reading a transponder attached to or embedded in the special characteristic of an object (e.g., cargo identification, pet identification, taxi identification at an airport, and the like).
Generally, all existing transponder electronic readers of such radio frequency identification systems utilize proprietary systems. That is, a card from one system will not be readable by a system provided by another vendor. In some systems, the transponder object emits a signal modulated by frequency shift keying (FSK), i.e., the binary transmission is represented by a mark and a space which correspond to the 1 and 0 of the binary signal, the mark and space being signals on two separate frequencies (e.g., xe2x85x9 and {fraction (1/10)} of the frequency of the RF interrogation signal). Other systems utilize phase shift keying (PSK) as well known in the art. Systems using PSK modulation cannot read the cards which transmit FSK modulated information and systems which read FSK modulated information cannot read the cards which transmit PSK modulated information.
While all such transponder electronic readers read matching transponder objects, in most systems they are also required to communicate with a controller of some sort. The controller generally comprises a central processing unit (CPU) which may interact with a number of such readers which are simultaneously connected to it. A number of different systems have evolved over the years for communicating data from a reader to a controller. Some of these systems, or communications protocols, are known as magnetic stripe communications protocol, Wiegand communications protocol, single wire Wiegand communications protocol, RS232 communications protocol, RS422 communications protocol, and the like. These various communication protocols generally require 1, 2, 3 or more electrical wire connections between the transponder electronic reader and the controller. Furthermore, the data modulation schemes for these various systems differ as well known to those of ordinary skill in the art. This has led to a problem in the industry in the stocking of transponder electronic readers. In order to stock transponder electronic readers which are compatible with the various communications protocols employed by the various controllers, one needs to stock many transponder electronic readers which are mutually incompatible with one another. A need, therefore, exists for an transponder electronic reader which is capable of working with a number of different communication protocols in communicating with a corresponding controller so as to reduce the inventory requirements for transponder electronic readers.
It is also desirable to have the transponder electronic reader require as little field programming as possible. In this way, relatively unskilled personnel may successfully install transponder electronic readers and have them operate with corresponding controllers and transponders with relatively little difficulty. To avoid the necessity to physically program such readers to communicate using a given communications protocol (as by setting DIP switches or jumpers) would be highly desirable.
In certain security and access control situations it would be desirable to do more with the transponder than merely sense the presence of the transponder. Similarly, in any kind of access control system, it would be desirable to provide a user of the access control system with the ability to communicate special signals via a reader without requiring an extensive user interface on the reader which might be subject to vandalism or misuse.
Accordingly, it is an object and advantage of the present invention to provide an improved RF identification system.
It is a further object and advantage of the present invention to provide an improved transponder electronic reader for use in an RF identification systems.
It is a further an object and advantage of the present invention to provide a capability to program the transponder reader to communicate with an attached controller using a communications protocol specified by information contained in an output format identification portion of the identification signal stored in the transponder and transmitted to the transponder reader.
It is a further object and advantage of the present invention to provide an improved transponder for use in an RF identification system.
It is a further object and advantage of the present invention to provide a transponder for use in an RF identification system which contains an identification signal which has within it, in addition to an authorization code number, an output format identification portion which, when transmitted to and received by the transponder reader, defines the communications protocol to be used by the transponder reader in communicating with attached devices such as a controller.
Yet another object and advantage of the present invention is the provision of a transponder reader capable of reading both PSK and FSK signals.
Yet another object and advantage of the present invention is the provision of a mechanism by which either the PSK or the FSK mode of operation may be normally disabled and easily authorized in an accountable manner.
It is a further object and advantage of the present invention to provide an improved electronic reader having a detector, a timer and, optionally, a counter capable of producing signals in response to:
a) the detection of the object within the field of inspection of the reader,
b) presence of the object within the field of inspection for a fixed period of time exceeding a minimum threshold.
c) the presentation of the object to the field of inspection a given number of times within a minimum threshold period of time.
These and many other objects and advantages of the present invention will become apparent to those of ordinary skill in the art from a consideration of the drawings and ensuing description of the invention.
An object identification system and method detects the presence of a target object in a field of inspection and in one aspect of the invention, generates a first signal if the object is left in the field of inspection for more than a minimum threshold period of time. In a second aspect a second signal is generated if the object is introduced to the field of inspection more than a minimum threshold number of times (having been withdrawn from the field of inspection in the interim) within a minimum threshold period of time.